12. Photovoltaic power plants produce electricity from sunlight. As a result of astonishing recent technological advances, the cost of producing electric power at photovoltaic power plants, allowing for both construction and operating costs, is one-tenth of what it was 20 years ago, whereas the corresponding cost for traditional plants, which burn fossil fuels, has increased. Thus, photovoltaic power plants offer a less expensive approach to meeting demand for electricity than do traditional power plants.

The conclusion of the argument is properly drawn if which one of the following is assumed?

(A) The cost of producing electric power at traditional plants has increased over the past 20 years.

(B) Twenty years ago, traditional power plants were producing 10 times more electric power than were photovoltaic plants.

(C) None of the recent technological advances in producing electric power at photovoltaic plants can be applied to producing power at traditional plants.

(D) Twenty years ago, the cost of producing electric power at photovoltaic plants was less than 20 times the cost of producing power at traditional plants.

(E) The cost of producing electric power at photovoltaic plants is expected to decrease further, while the cost of producing power at traditional plants is not expected to decrease.

E seems best.

I vote for C.

D it is

vote for D

20 times?

i dont think we need 20 times less than..whatever..

The missing info here is ..we dont know if photo plants are actually cheaper than traditional plants..all we know is the cost is one-tenth of what it was 20 years ago... D provides that "LINK" by saying that photo plants costs less. But i still dont get why 20 times is needed.

But the information in D is about 20 years ago.
How do we conclude it is cheaper today ?

Well D says that, 20 yrs ago cost of photovoltaic plant for about (less than) 20 times more than traditional plant. Say it was 10 times.

At present time, it has become 1/10th that means it is same as what a traditional plant cost 20 yrs ago. But the stem also says that the cost of traditional plant has increased. Now putting it together, we can see that the cost of traditional plant actually is say 2 times what it was 20 yrs ago. Comparing it to the photovoltaic cost today, it is obvious to use the cheaper photovoltaic plant.

does this make things clearer.